Fig. 2. Galactosyltransferase activity and LPG biosynthesis in the OB1 mutant. (A) Microsomal membranes were prepared from promastigotes of WT, OB1 and OB1 transfected with an LPG3 expression construct (OB1 + LPG3; cosOB1-AΔHindIII; see Figure 3C). Galactosyltransferase activity was assayed using endogenous LPG acceptors and UDP-[³H]galactose donor as described in Materials and methods, either directly, or in the presence of 0.1% Triton (OB1 + Triton), or of an equal mixture of WT and OB1 membranes (OB1 + WT). (B) Lysates corresponding to 10⁶ log phase promastigotes were analyzed by western blotting with the anti-PG antibody CA7AE. The samples were WT, OB1 or OB1 transfected with an LPG3 expression construct (pXG-LPG3-GFP+). The arrow marks the interface between the stacking and separating gel, and the positions of PPG and LPG are marked.